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| Daylily rust | |
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| Puccinia hemerocallidis | |
Puccinia hemerocallidis (Daylily rust)
Puccinia hemerocallidis von Thümen is a macrocyclic heteroecious pathogenic fungus, causing rust disease in daylilies. Its main hosts are plants from genus Hemerocallis (H. flava, H. fulva, H. longituba, H. minor, H. thunbergii ) and alternate hosts are Patrinia spp[1]. The symptoms are leaf lesions appearing as chlorotic areas on both surfaces of the leaf 7-10 days after infection. They grow in size and amount and start to produce orange-yellow spores. It can lead to ultimatelly death of foliage.
Ecology
During summer period yellow-orange urediospore penetrates leaf surface of daylily and forms mycelium within the leaf, eventually erupting and spreading numerous urediospores[2]. Uredia germinate mostly on the lower leaf surface, but can also be on the upper. This cycle repeats several times, amplificating daylily infection, untill in autumn telia grow among uredia. Early on they are honeybrown, gradually darkening through reddish-brown to blackish. Teliospores overwinter in dead daylily leaves and in spring germinate to produce basidioapores. Basidiospores are dispersed by wind or by animals. They cannot infect daylilies, but need an alternate host Patrinia spp. to form spermogonia. Spermogonia then produce spermatia (also called pycniospores), which fertilize hyphae of the opposite mating type in spermogonia. This is the sexual stage of parasite life cycle. After that aecia are formed on the lower surface of Patrinia's leaf and begin to produce light yellow aeciospores. Those aeciospores, when reaching the daylily leaves with wind or by other means, germinate through the leaf and again form uredia, completing the life cycle of pathogen.
In warm climate, where daylilies are perennial, rust does not depend on alternate host and sexual spermatial stage, and can reproduce asexually via urediospores.
Certain environmental conditions are necessary to provide rust infection in daylilies[3]. Temperature around 22°C and about 5 hours of leaf wetness are optimal for lesion formation. No lesion formation was observed at 36°C and above in greenhouse experiments, and at the temperature of 10°C and less the amount of developing lesions dicreased significantly. However, once rust has established, the disease development is no more sensitive to humidity or temperature.
History
Puccinia hemerocallidis was initially described in 1880 by von Thümen[4], who observed its talial stage on the leaves of Hemerocallis flava in Siberia. He reported the disease that attacks leaves and scapes of this daylily. Dietel[5] described its uredinial stage on Hemerocallis longituba in Japan in 1898.
Geography
P. hemerocallidis originates from Asia. Its native range includes Siberia, Korea, Japan, Taiwan and China. With international trading of daylilies, P. hemerocallidis expanded across the world and became invasive in many countries. According to EPPO distribution map[6], to date it has been reported in Brazil[7], USA[8], Australia, Portugal, Columbia, Vietnam, Thailand, Taiwan and South Africa.
Methods of control
Resistant cultivars
To date the number of daylily cultivars registered with the American Hemerocallis Society is nearly 80,000. Some of them are not susceptible to daylily rust. Mueller et al.[9] examined 84 commercially important daylily cultivars for resistance to P. hemerocallidis inoculation. They classified 14 (17%) of them as resistant, 13 (15%) as moderately resistant, 22 (26%) as moderately susceptible, and 35 (42%) as fully susceptible. They recommended several cultivars with very high levels of resistance to be utilized by breeders to create resistant to daylily rust cultivars. Prairie Blue Eyes, Carolyn Criswell, Mardi Gras Parade, Hush Little Baby, Green Flutte, Plum Perfect cultivars showed the most remarkable resistance in their greenhouse assay, with no signs of disease 21 days after inoculation. Identification of genetic traits of those cultivars responsible for resistance thus is important task for future research. Resistant cultivars are the most effective way to fight rust epidemics.
Fungicides
Fungicides are one of the most effective methods for managing daylily rust. Among them azoxystrobin or pyraclostrobin (Fungicide Resistance Action Committee [FRAC] group 11), chlorothalonil (FRAC group M5), myclobutanil, propiconazole, and triadimefon significantly reduced lesion development when applied up to 15 days before inoculation[10]. Azoxystrobin could also significantly reduce lesion formation when applied 7 days postinoculation in the same study. In another research azoxystrobin remarkably dicreased disease severity for up to 9 weeks after inoculation when applied as a soil drench and as a root dip[11] Available fungicides can to be used in rotation on 7-, 14-, 21-, or 28-day intervals.
EPPO phytosanitary measures
In 2007 EPPO added P. hemerocallidis to the A2 List, and recommended endangered EPPO countries to manage it as a quarantine pest. EPPO therefore considers excluding the pathogen from the greater region, where it has not been yet found, as the best strategy. It recommend to require all imported plants for planting of Hemerocallis (and possibly also Patrinia as an alternate host) to originate from a pest-free area[12].
Economic impact
Daylilies are highly valued worldwide as ornamental plants. Daylily rust can lead to ultimate foliage death and spreads rapidly. Eradication of infected stocks, fungicide implications and quarantins significantly affect daylily market. Little is known to date about commercial importance and negative impact of daylily rust for nurseries or for gardeners in its native range. Intriguingly, in Japan P. hemerocallidis affect mostly wild Hemerocallis populations, but there were no reported outbreaks for daylily cultivars. The reason is uncertain[2]. In North America it became widespread and causes serious problems. After it has been reported in 2000, mandatory quarantine was enforced by federal and state regulatory agencies. This and other eradication measures were costly for growers. However, the disease widespread quickly and by 2003 quarantine was recognised uneffective and abolished[2].
- ^ "Puccinia hemerocallidis (PUCCHM)[Overview]| EPPO Global Database". gd.eppo.int. Retrieved 2018-10-09.
- ^ a b c Buck, J.W.; Ono, Y. (2012). "Daylily rust". The Plant Health Instructor. doi:10.1094/phi-i-2012-0516-01. ISSN 1935-9411.
- ^ Mueller, D. S.; Buck, J. W. (2003-04). "Effects of Light, Temperature, and Leaf Wetness Duration on Daylily Rust". Plant Disease. 87 (4): 442–445. doi:10.1094/pdis.2003.87.4.442. ISSN 0191-2917.
{{cite journal}}: Check date values in:|date=(help) - ^ von Thümen F, Moskovskoe obshchestvo liubitelei prirody. (1880). "Contributions to the fungus flora of Siberia". Bulletin de la Société impériale des naturalistes de Moscou. (in German). t.55:no.1-4 (1880): 72–104.
- ^ Dietel P (1898). "Some rusts from eastern Asia". Hedwigia (in German). v.37 (1898): 212–218.
- ^ "Puccinia hemerocallidis (PUCCHM)[World distribution]| EPPO Global Database". gd.eppo.int. Retrieved 2018-10-10.
- ^ Inokuti, E. M.; Soares, D. J.; Barreto, R. W. (2012-01-10). "Epidemic spread of Puccinia hemerocallidis in Brazil". Australasian Plant Disease Notes. 7 (1): 7–8. doi:10.1007/s13314-011-0033-7. ISSN 1833-928X.
- ^ Hernández, José R.; Palm, Mary E.; Castlebury, Lisa A. (2002-11). "Puccinia hemerocallidis, Cause of Daylily Rust, a Newly Introduced Disease in the Americas". Plant Disease. 86 (11): 1194–1198. doi:10.1094/pdis.2002.86.11.1194. ISSN 0191-2917.
{{cite journal}}: Check date values in:|date=(help) - ^ Mueller, Daren S.; Williams-Woodward, Jean L.; Buck, James W. (2003-10-01). "Resistance of Daylily Cultivars to the Daylily Rust Pathogen, Puccinia hemerocallidis". HortScience. 38 (6): 1137–1140. ISSN 0018-5345.
- ^ S. Mueller, D; Jeffers, Steven; Buck, James (2004-06-01). "Effect of Timing of Fungicide Applications on Development of Rusts on Daylily, Geranium, and Sunflower". Plant Disease - PLANT DIS. 88: 657–661. doi:10.1094/PDIS.2004.88.6.657.
- ^ Dong, W. B.; Jeffers, S. N.; Buck, J. W. (2013-07). "Management of Daylily Rust with Different Fungicides and Application Methods". Plant Disease. 97 (7): 921–926. doi:10.1094/pdis-12-12-1127-re. ISSN 0191-2917.
{{cite journal}}: Check date values in:|date=(help) - ^ "Puccinia hemerocallidis". EPPO Bulletin. 39 (1): 48–50. 2009-04. doi:10.1111/j.1365-2338.2009.02235.x. ISSN 0250-8052.
{{cite journal}}: Check date values in:|date=(help)